Mr. K. G. is a thin 60-year-old man admitted to the hospital for cardiac cathete

Question

Mr. K. G. is a thin 60-year-old man admitted to the hospital for cardiac catheterization for recurrent angina. Past medical history includes hypertension, type 2 diabetes mellitus, and a previous myocardial infarction 2 years ago. Current medications are metformin (Glucophage), glipizide (Glucotrol), enteric-coated aspirin (Ecotrin), and lisinopril (Zestril). Laboratory tests on admission revealed the following: normal electrolyte levels; blood urea nitrogen (BUN), 40 mg/dL; and serum creatinine, 2.0 mg/dL. A complete blood cell count and urinalysis were unremarkable. Mr. K. G. receives intravenous fluids at a KVO (keep vein open) rate (20 mL/hr) on the morning of the procedure. He successfully undergoes the catheterization and returns to the telemetry unit. The day after the procedure, Mr. K. G.’s urine output decreases to less than 10 mL/hr. Mr. K. G. is given a fluid bolus of normal saline without any increase in urine output. Furosemide is administered intravenously, with a slight increase in urine output to 15 mL/hr for several hours. Laboratory studies reveal the following: potassium, 5.9 mEq/L; BUN, 70 mg/dL; serum creatinine, 7.1 mg/dL, and carbon dioxide total content, 16 mEq/L. The next day Mr. K. G. has 2+ edema and basilar crackles, and he complains of feeling short of breath. A preliminary diagnosis of acute renal failure is made.

Questions

What are possible factors predisposing Mr. K. G. for acute renal failure?
What laboratory studies would be useful to assist in the diagnosis of acute renal failure? Describe expected results for a patient with acute tubular necrosis.
What medical interventions do you anticipate for Mr. K. G.?
What interventions could have been taken before Mr. K. G.’s cardiac catheterization to possibly ¬prevent his acute renal failure?

Explanation / Answer

What are possible factors predisposing Mr. K. G. for acute renal failure?

There are multiple predisposing risk factors for Acute Renal Failure (ARF) for Mr. K.G. One of the most important predisposing factors is his baseline renal function (His admission creatinine level was 2.0 mg/dl and BUN was 40 mg/dl). Baseline creatinine concentrations 1.5 mg/dL and high urea concentrations are independently associated with the development of ARF.

There are also procedural predisposing risk factors for the development of ARF which include the volume of contrast medium (Iohexol), and periprocedural hemodynamic alterations, contrast-induced nephrotoxicity, drug-induced toxicity, and/or atheroembolism.

Contrast-induced nephropathy was defined as an increase of 25% or 0.5 mg/dL in serum creatinine concentrations 48 hours after the procedure.

The other risk factors include his past health status (Past medical history) - diabetes mellitus, hypertension, his age. Besides this, the intake of multiple drugs (especially non-steroidal anti-inflammatory drugs (Ecotrin) and Angiotensin Converting Enzyme (ACE) inhibitors (Lisinopril)) and the duration of medication therapy predispose him to impaired renal function and ARF.

What laboratory studies would be useful to assist in the diagnosis of acute renal failure? Describe expected results for a patient with acute tubular necrosis.

Acute Kidney Injury (AKI)/ARF is suspected when urine output falls or serum BUN and creatinine rise.

Further workup should be done to identify the type of ARF and its cause. The usual blood tests include Complete Blood Count (CBC), BUN, creatinine, electrolytes (including calcium and phosphate). Urine tests include sodium and creatinine concentration and microscopic analysis of sediment.

A progressive daily rise in serum creatinine is diagnostic of ARF. Serum creatinine can increase by as much as 2 mg/dL/day. Urea nitrogen may increase by 10 to 20 mg/dL/day.

The expected results for a patient with Acute Tubular Necrosis (ATN) include:

What medical interventions do you anticipate for Mr. K. G.?

What interventions could have been taken before Mr. K. G.’s cardiac catheterization to possibly prevent his acute renal failure?

Early intervention of renal insufficiency: Looking for risk factors and reviewing the indications for the administration of contrast medium could have prevented ARF. Most risk factors can be detected by history taking and physical examination. As the patient has multiple risk factors for ARF, it must have considered before proceeding with cardiac catheterization. This includes infusion of normal saline IV for 4 to 6 hours before the procedure and 6 to 12 hours afterward.

Use of low-osmolar or iso-osmolar contrast: According to the statement of Weisbord and Palevsky, efforts to find effective preventive interventions for contrast-induced nephropathy should focus on four principal strategies:

(1) Administration of less nephrotoxic contrast agents.

(2) Provision of pre-emptive renal replacement therapy to remove contrast from the circulation.

(3) Utilization of pharmacological agents to counteract the nephrotoxic effects of contrast media and

(4) Expansion of the intravascular space and enhanced diuresis with intravenous fluids.

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